Inertial locking retractors have a substantially long history and were first applied to seat belts and safety harness in the aircraft industry with considerable increase preceding and during World War II. Such structures were intended to provide maximum freedom of movement for pilots and users while providing substantially instantaneous protection under emergency conditions which cause an inertially sensed imbalance. Some of such devices were webbing sensitive and locked on accelerated withdrawal of the webbing. Others of such devices were vehicle sensitive so that locking occurs when an inertial imbalance occurs in the vehicle or aircraft. The latter devices for the most part involved pendulum structures which were position sensitive and responding to change of acceleration in the principal line of travel or were omnidirectionally sensitive in that inertial imbalance from any direction in the plane of the vehicle would move the sensor pendulum and cause the lock-up of associated retractor structure, thus stopping any further webbing withdrawal and thus restraining the user from projection from his seat or position.
In the present invention, the object is to provide a pendulum to accomplish omnidirectional inertial sensing and where the mechanical movement of the novel pendulum structure acts directly on a lever or latch bar to prevent withdrawal of webbing from a retractor drum by engaging the pawl element against a ratchet wheel which is a part of the retractor reel.
When the words, "Bell Pendulum" are used herein, they are intended to describe succinctly a hollow form in somewhat the shape of a truncated cone closed and flatted at the smaller end and open at the larger end and in which the mass is so distributed as to place the center of gravity well below the smaller end and concentrated adjacent the lower perimeter or skirt. The material of construction may be metal or resin. In some instances a composite construction could be desirable, the bell pendulum being in an injection molded plastic and having attached thereto a high specific gravity ring or annulus to concentrate the mass at or adjacent to the skirt perimeter.